$($i$)$ In a transformer machine which of the following statements is true? $[3$ points$]$

A$.$ The current in the primary winding is ac and the current in the secondary winding is also ac$.$

B$.$ The current in the primary winding is ac and the current in the secondary winding is dc$.$

C$.$ The current in the primary winding is dc and the current in the secondary winding is ac$.$